Preview window stuttering, which transfers to recording stuttering

[PocketLogic]

OK, so this is a weird one...

Here's my setup -

Windows 11 Pro
Asus ROG Maximus Hero Z790 motherboard
Intel 13900K
Asus RTX 4090
4 x Samsung 980 Pro SSD's running at Gen 4 speeds
Corsair Vengeance DDR5 (4 x 32GB) running at 5600MT's
2 x LG 38GN95B Widescreen monitors @ 120hz (down clocked for a reason - see below)
OBS is always run as Admin

I am attempting to record video using the "Display Capture" setting. Both monitors are set to 120hz, and I have the recording settings set to record at 120FPS, just to make sure they sync up during a recording. However, the issue isn't with recording, it's with the preview window.

I noticed this morning that the preview window in OBS was very smooth when previewing the "Display Capture" window, but would sometimes stutter a bit before going back to being smooth. Again, this isn't during a recording, this is the actual preview window that's stuttering. The preview window is supposed to capture anything in that window, right? Therefore, it makes perfect sense that when I try to record something, I get the same results as the preview window. Most of the time, it's perfectly smooth in that window, but there's random instances where that preview window is stuttering slightly, and this, of course, transfers to the recording.

I have OBS on one monitor, and the "Display Capture" is set to record the other monitor. The preview window is set to 1280 x 720 (which is the size of the window I am capturing). Again, OBS is NOT recording yet, and that preview window has a slight stuttering to it, randomly. Most of the time, it's perfectly smooth. This is what got me thinking that it isn't the OBS recording that's causing the stuttering I'm seeing in my videos. It's the actual preview window, and since OBS is recording whatever is in that window, if that window stutters, it'll show up in the video.

So then, I said to myself "If it's the preview window causing that stuttering, then just disable the preview window while recording..". Nope. The recordings still show a slight stuttering randomly, as if the frame rate is lowering itself slightly to be out of sync with the 120hz monitor and the 120fps that I set as the recording fps. But it's also happening in the preview window, while not recording, so I'm at a loss as to what's actually causing this behavior.

The actual "Display Capture" that I am previewing/recording is 100% smooth 100% of the time, so it's not what I'm recording or previewing, it's an issue with OBS. Or, at least that's my best guess at this point. I've attached a log file.

Could this be an issue with VSYNC? At the moment, all of my monitors are GSYNC compatible, but I have that turned off in the NVidia control panel. It's set to "Fixed Refresh". VSync is set to "Application-Controlled". I don't know why VSYNC would be the cause here if the thing I am capturing is 100% smooth, but the preview window sometimes isn't.. So, VSYNC being the cause seem unlikely, but I'm no expert.

 

[koala]

According to your log, all your three monitors are running with 144 Hz, while you're trying to record with 120 fps. This requires 144-120 = 24 frames to be omitted from the video, which is one frame every 120/24 = 5 frames. This will be perceived as unsmooth video, but I would not go so far as to say that's stutter.

If the recording process itself is good or leads to frame drops isn't visible in the log, because you use custom ffmpeg output, which omits almost all logging. Recommendation: switch to simple output mode and select the "indistinguishable quality, large file size" quality.

 

[PocketLogic]

According to your log, all your three monitors are running with 144 Hz, while you're trying to record with 120 fps. This requires 144-120 = 24 frames to be dropped, which is every 120/24 = 5 frame. This will be perceived as unsmooth video, but I would not go so far as to say that's stutter.

If the recording process itself is good or leads to frame drops isn't visible in the log, because you use custom ffmpeg output, which omits almost all logging. Recommendation: switch to simple output mode and select the "indistinguishable quality, large file size" quality.

Yeah, the log indicates they're running at 144hz, so this log must be from an older session. The dates on the logs are confusing, so I think I mixed them up. I ran the most recent test with all three monitors at 120hz. I'll see if I can attach the correct log file.

I'll do some tests with simple output mode and see if that helps.

 

[PocketLogic]

Here's a new log file with the correct 120hz for all monitors, and the settings you suggested. It still stutters in the preview Window, and not the actual thing I'm capturing, and it still does it without recording (and while recording). I don't know why the preview would be stuttering, other than the fact that there could be a discrepancy between the framerate of the thing I am previewing/recording (which is hard capped at 120FPS and never goes below that) and the preview window of OBS.

What I find strange is the fact that on one screen (the thing I am previewing/recording) it's perfectly smooth, and in OBS it isn't at times. It only does this for a few seconds, then things smooth out. It almost looks like a VSync issue, where the framerate is being halved for a few seconds, then returns to normal, but only in OBS's preview window.

 

[koala]

There were no errors for your recording. No lagged or lost frames. Should be flawless. Did you try a different media player such as VLC? The internal media player of Windows isn't the best and might fail with some media with higher bandwidth.

 

[PocketLogic]

There were no errors for your recording. No lagged or lost frames. Should be flawless. Did you try a different media player such as VLC? The internal media player of Windows isn't the best and might fail with some media with higher bandwidth.

Again, it's not the actual videos that are stuttering (well, they do, but as a result). It's OBS that's showing the stuttering in the preview window. If I record a video using OBS, the video will stutter at the exact same spot and time duration that it stuttered in the preview window during recording. The thing I am recording is flawless (perfectly 100% smooth).

I never use anything but VLC. Always have ;-)

 

[PocketLogic]

I've managed to get the recording to smooth out by doing a "Display Capture", but at full screen size. I'm a game developer, and I've been testing my game at normal size (1280x720), and then just shrinking the preview window down to capture the game window. I decided to try and switch the game window to full-screen-windowed mode, and just capture the display at full screen resolution and just scale down the output.

The preview window is still slightly choppy at times, but the recording is smooth, so at least the output is what I want.